Decomposers, Mutualists, and Killers Fungi Decomposers, Mutualists, and Killers

Fungi Fungi (most) degrade dead organic matter form nutritional partnerships with most vascular plants & some algae are pathogens of some plants & animals

parasitic fungi Figure 31.1

Fungi Fungi are absorptive heterotrophs saprobic mutalistic parasitic predatory (rarely)

predatory fungus Figure 31.5

fungal hyphae Figure 31.3

Fungi Fungal growth forms yeasts are unicellular most fungi produce multinucleate hyphae high surface area for absorption coenocytic or septate chitinous cell walls mycelia are massed hyphae

c o n i d I a Figure 31.12

budding yeast Figure 31.2

Fungi Fungal reproduction asexual reproduction sporangia - chambers producing haploid spores conidia - naked spores on hyphal tips binary fission or budding fragmentation

Fungi Fungal reproduction sexual reproduction between haploid hyphae of different mating types fusion of haploid hyphae (plasmogamy) produces dikaryotic (n+n) hyphae (heterokaryon) dikaryotic nuclei eventually fuse (karyogamy) to produce zygote meiosis produces haploid spore nuclei

Fungi Phylogeny four phyla differ in presence of septa in hyphae sexual reproductive structures methods of sexual spore formation DNA sequencing agrees that the four phyla are monophyletic

Fungi Phylogeny deuteromycetes are fungi without sexual reproductive data a polyphyletic “holding category” new techniques are assigning deuteromycetes to the four phyla

fungal phylogeny Figure 31-6

fungal classification Table 31.1

Fungi Phylum Chytridiomycota earliest diverging fungal group aquatic parasitic or saprobic (rarely mutualistic) unicellular or mycelial haploid or diploid, none dikaryotic

Fungi Phylum Chytridiomycota reproduction in Allomyces haploid zoospore germinates to produce haploid body haploid body produces male and female gametangia gametangia produce haploid gametes [flagellated gametes and zoospores is a unique (ancestral?) character]

Fungi Phylum Chytridiomycota reproduction in Allomyces pheromone attracts male gamete to female fusion of gamete nuclei produces zygote zygote grows into diploid body diploid body produces many diploid zoospores diploid zoospores produce more diploid bodies

Fungi Phylum Chytridiomycota reproduction in Allomyces diploid bodies produce resting sporangia meiosis within resting sporangia produces haploid zoospores alternation of generations

Allomyces sp. gametangia forming haploid gametes Figure 31.7

Fungi Phylum Zygomycota mostly coenocytic haploid except zygote entirely nonmotile some participate in mycorrhizal association with plants familiar example: Rhizopus stolonifer

Pilobolus sp. sporangiophores topped with sporangia Figure 31.8

sporangium shedding spores Figure 31.9

Fungi Phylum Zygomycota reproduction asexual spores are produced on stalked sporangiophores bearing single or multiple sporangia sexual reproduction occurs between hyphae of different mating types

Fungi Phylum Zygomycota reproduction sexual reproduction pheromones cause hyphae to grow toward each other gametangia are produced and fuse into a zygosporangium gametes (1n) fuse into a zygote (2n)

Fungi Phylum Zygomycota reproduction sexual reproduction meiosis produces zygospores (1n) inside the resistant zygosporangium after dormancy, zygosporangium releases zygospores zygospores germinate to produce haploid hyphae

Zygomycete life cycle Figure 31.9

Fungi Phylum Ascomycota large diverse group (~30,000 spp.) saprobes, parasites, mutualistic symbionts hyphae segmented by porous septa produce sexual spores in asci (sacs)

Fungi Phylum Ascomycota two major subgroups Hemiascomycetes mostly unicellular (yeasts) or microscopically multicellular asexual reproduction by fission or budding

Fungi Phylum Ascomycota Hemiascomycetes sexual reproduction fusion of haploid cells of different mating types [+/- mitotic population growth] meiosis produces four haploid nuclei [+/- mitosis to produce eight] ascospores in the original cell = ascus

Fungi Phylum Ascomycota Hemiascomycetes familiar example = Saccharomyces cerevisiae (baker’s, brewer’s yeast)

Fungi Phylum Ascomycota Euascomycetes mycelia of septate hyphae multicellular sexual fruiting bodies: ascocarps asexual reproduction by conidia

Fungi Phylum Ascomycota Euascomycetes sexual reproduction mating structures form on two compatible mating types haploid nuclei from the “male” enter the female mating structure the dikaryotic mating structure produces ascogenous hyphae

Fungi Phylum Ascomycota Euascomycetes sexual reproduction tips of n+n hyphae form asci in asci, haploid nuclei fuse meiosis produces four haploid nuclei [+/- mitosis to form 8 haploid nuclei] spores are formed and released

characteristic ascomycete reproductive sacs Figure 31.10

Ascomycete life cycle Figure 31.13

Fungi Phylum Ascomycota Euascomycetes familiar examples Neurospora crassa bread mold used by Beadle and Tatum brightly colored cup fungi morels & truffels Penecillium spp. Aspergillus spp.

Figure 31.11

Fungi Phylum Basidiomycota large diverse group (~25,000 spp.) saprobes, parasites, mutualistic symbionts produce sexual spores on basidia

Fungi Phylum Basidiomycota familiar examples puffballs bracket fungi mushrooms and toadstools, edible and toxic bird’s nest fungi jelly fungi smut and rust fungi

Basidiomycetes Figure 31.14

Fungi Phylum Basidiomycota sexual reproduction basidiospores germinate to produce haploid, septate hyphae hyphae of different mating types fuse to form dikaryotic hyphae dikaryotic hyphae eventually produce a characteristic basidiocarp

Fungi Phylum Basidiomycota sexual reproduction basidiocarp bears surfaces covered with basidia two nuclei in n+n basdium fuse to form 2n zygote meiosis produces four basidiospores basidiospores are displayed on tip of basidium and released

basidiomycete life cycle Figure 31.15

Fungi Fungal Mutualisms with plants mycorrhizae endomycorrhizal fungi are within the root ectomycorrhizal fungi are outside the root fungal symbiont enhances absorption of water and some nutrients by photosymbiont photosymbiont provides carbohydrate to fungal symbiont

Fungi Fungal mutualisms with plants lichens (~13,500 spp.) partnerships between fungi and green algae or cyanobacterium fungal symbionts are usually ascomycetes lichen are classified as distinct organisms among the hardiest organisms

Fungi Fungal mutualisms with plants lichens critical primary producers in arctic ecosystems fungal symbiont provides mineral nutrients photosymbiont provides fixed carbon among the most environmentally sensitive organisms

Fungi Fungal mutualisms with plants lichens three general growth forms crustose - crust-like foliose - “leafy” fruticose - “shrubby”

crustose, foliose, fruticose lichens Figure 31.17

Fungi Fungal mutualisms with plants lichens reproduction fragmentation of thallus some fungal symbionts produce ascospores or basidiospores

Fungi Fungal mutualisms with plants lichens reproduction fragmentation of thallus some fungal symbionts produce ascospores or basidiospores soredia

reproduction by soredia Figure 31-18